Utility lines for water, electricity, gas, telephone and cable television are often run underground for safety and aesthetics reasons, among others. Sometimes the underground utilities are buried in a trench that is then back filled. Trenching, however, can be time consuming and can cause substantial damage to existing structures or roadways. Consequently, horizontal directional drilling (“HDD”) is often used to avoid these drawbacks.
A typical horizontal directional drilling machine includes a frame on which is mounted a rotational drive mechanism. The rotational drive mechanism can be slidably moved along the longitudinal axis of the frame, to rotate a drill string about its longitudinal axis while sliding along the frame to advance the drill sting into, or withdraw it from, the ground. The drill string comprises one or more drill rods attached together in a string.
A boring tool is installed onto the advancing end of the drill string (i.e., the end furthest away from the HDD machine). More specifically, a drill bit is used when the drill string is being advanced into the ground. On the other hand, a back reamer is used to enlarge a bored hole and is used when the drill string is being withdrawn after a hole is cut. Boring tools may include a wide variety of soil cutting devices tailored for specific formations. Examples include cutting edges that shear the soil and compression elements that concentrate longitudinal force from the drill string into a concentrated area to fracture the ground when boring in rock conditions.
Boring machines can include controls that allow the operator to control both the rotational movement and the longitudinal movement, longitudinal movement associated with thrust. The optimum setting of rotational movement and thrust movement depends on various factors such as the soil conditions, the formation, and the type of boring tool. The boring process generally requires maintaining consistent thrust pressures and at a low thrust speed control. In many systems, the software uses adjustable thrust and rotation pressure set-points. If either the thrust or rotation pressure exceeds its set-point, then the thrust/pullback speed may be manually reduced to control the pressure which has exceeded its set-point. This requires the operator to continuously monitor the pressure set-points and adjust them as drilling conditions change. Therefore, there exists a need in the art for a method and apparatus to automate portions of the drilling operation.